package com.wtx.chapter10;

import java.util.TreeMap;

/**
 * @description: 字典树
 * @author: wtx
 * @createDate: 2020/5/28
 */
public class Trie {

    private class Node{
        public boolean isWord;
        public TreeMap<Character,Node> next;

        public Node(boolean isWord) {
            this.isWord = isWord;
            next = new TreeMap<>();
        }

        public Node() {
            this(false);
        }
    }

    private Node root;
    private int size;      //不是结点的数量，而是单词的数量

    public Trie() {
        root = new Node();
        size = 0;
    }

    public int getSize(){
        return this.size;
    }

    //添加一个单词 word
    public void add(String word){

        Node cur = root;
        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            if (cur.next.get(c) == null)
                cur.next.put(c,new Node());
            cur = cur.next.get(c);
        }
        //添加完毕，但当前cur不一定是叶子结点
        if (!cur.isWord){
            cur.isWord = true;
            size++;
        }
    }

    //查询单词
    public boolean contains(String word){

        Node cur = root;
        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            if (cur.next.get(c) == null)
                return false;
            cur = cur.next.get(c);
        }
        return cur.isWord;
    }

    //查询Trie中是否有单词以prefix为前缀
    public boolean isPrefix(String prefix){

        Node cur = root;
        for (int i = 0; i < prefix.length(); i++) {
            char c = prefix.charAt(i);
            if (cur.next.get(c) == null)
                return false;
            cur = cur.next.get(c);
        }
        return true;
    }
}







